A toxicological study was conducted to evaluate the potential
conflict between extended consumption of hemp food products and
workplace drug-testing programs in the United States. Fifteen
volunteers ingested hemp/canola oil blends containing four
different concentrations of delta-9-tetrahydrocannabinol (THC),
each over a 10-day period. Corresponding THC doses ranged from
0.09 to 0.6 milligrams per day. Two urine samples were collected
at the end of each period and analyzed for THC metabolites by
immunoassay and GC/MS (gas chromatography/mass spectroscopy).
Samples were also collected prior to the test and on days 1 and 3
after the last oil had been ingested.

The analyses showed that daily THC doses of 0.45 mg did not
cause exceedance of the 50 parts per billion (ppb) cutoff used by
federal programs to evaluate the outcome of immunoassay screening
tests. Confirmation of these samples by GC/MS consistently found
THCCOOH levels less than 5 ppb, with the exception of one sample
confirmed at 5.2 ppb. This is significantly below the 15 ppb
cutoff for confirmation under federal programs. THC doses as low
as 0.2 mg/day caused several exceedances of the more stringent 20
ppb screening cutoff used by few employers and law enforcement
agencies. Yet all of these samples were confirmed at less than 5
ppb. One of three volunteers consuming up to 0.6 mg/day of THC
screened positive at the 50 ppb level but was confirmed at less
than 5 ppb.

The findings suggest that a conflict between hemp food
consumption and workplace drug testing is most unlikely if THC
levels in hemp oil and hulled seeds are maintained below 5 and
2 parts per million (ppm) respectively, and if drug testing
programs follow federal guidelines requiring that any urine
sample screening positive be confirmed by GC/MS.

Background

In recent years, food products made from or containing seeds
of the hemp plant (Cannabis sativa) have increasingly
become available in natural food stores in North America. Hemp
seeds offer several nutritional benefits. These include a
balanced fatty acid composition of the oil (desirable
omega-3/omega 6 ratio and presence of minor fatty acids such as
gamma-linolenic acid (GLA)), a reasonably complete amino acid
spectrum of the seed meat, and comparatively high concentrations
of vitamin E. Food items from hemp seeds include cold-pressed oil
used for cooking, in dressings, and in capsules as supplements.
Hemp oil is also used in a range of bodycare products, such as
creams, shampoos, soaps, and lip balms. The seeds are generally
hulled prior to use in snack bars, nut butters, and other
spreads, or sold in bulk for cooking and baking. A small amount
of whole seeds continues to be used in snacks. Since commercial
hemp farming was relegalized in Canada in 1998, the majority of
hempseeds and oil in the U.S., previously made from imported
Chinese birdseed, now originates in Canada and in the European
Union (EU). Commercial farming of hemp in the U.S. remains
prohibited under federal law.

The expansion of products from hemp seeds into their largest
potential North American market, the "natural foods"
sector in the U.S., now faces a significant obstacle. Flowers of
industrial hemp plants contain minute quantities of
delta-9-tetrahydrocannabinol (THC), the main psychoactive
ingredient in marijuana. Industrial hemp varieties grown in
Canada and the EU are bred to contain less than 0.3% THC in the
upper portion of the flowering plant. In comparison, marijuana
plants may contain 2-20% THC.

Depending on the hemp variety and the degree of seed cleaning,
various amounts of THC residues can be found on the outer shells
of whole seeds and in the products made from hemp seeds. The
presence of THC in hemp foods has raised concern over their
potential interference with employee drug-testing programs in the
U.S. Studies conducted in 19951997 showed that eating hemp
foods may in fact cause positive urine tests for marijuana.
However, these studies involved the consumption of products from
seeds with considerably higher THC levelsoften more than
100 micrograms per gram (µg/g) or parts per million
(ppm)than are now commonly found in commercial hemp seeds
in North America. Thus, these studies do not allow a realistic
assessment of the potential impact of such foods on the outcome
of employee drug tests. However, the
federal Drug Enforcement Agency (DEA) and the Office of National
Drug Control Policy cite the potential interference with
drug-testing programs as one of their main objections to the
importation and sale of hemp foods in the U.S.

Thorough cleaning of hemp seeds typically keeps THC levels in
oil and hulled seeds produced in Canada to less than 5 and 2 ppm,
respectively. Regulations in Canada, the main
supplier of hemp seeds to the U.S., limit THC levels in hemp seed
products to 10 parts per million (ppm). In the U.S., there is
currently no such standard for the concentration of THC in food
items.

Typical workplace drug testing
procedures for marijuana in the U.S.

A urine sampleannounced or randomis collected and
screened for THC metabolites, using an immunoassay test. Such
immunoassays can be performed rapidly and at low cost, yet they
are not highly specific for THCCOOH, the main metabolite of THC.
If a screening test detects THCCOOH above a specified
"cutoff" concentrationfederal workplace testing
programs apply a 50 nanograms/milliliter (ng/mL) or parts
per billion (ppb) cutoffthe sample is then
"confirmed" by the more specific GC/MS (gas
chromatography/mass spectroscopy) method. If GC/MS detects
THCCOOH at levels above the confirmation cutoff of 15 ppb, a
urine sample is considered "confirmed positive" for
marijuana. Some employers and law enforcement agencies in the
U.S. use a lower screening cutoff of 20 ppb and confirmation
cutoff of 10 ppb. Very few drug-testing programs rely solely on
the positive outcome of a screening test without automatic
subsequent confirmation testing by GC/MS.

Study Objective and Design

The objective of the present study was to reevaluate the
potential impact of hemp food consumption on the outcome of
workplace drug tests for marijuana. Specifically, the study was
designed to establish a correlation between extended daily
ingestion of THC via hemp food and the likelihood of failing
screening or confirmation tests of urine samples. The study
involved 15 adult THC-naïve volunteers (ages 2984, 10
female, 5 male). Each volunteer ingested, during four consecutive
10-day periods, daily THC doses ranging from 0.09 to 0.6
milligrams (mg), much below the typical 10 mg threshold for
psychoactivity from THC ingestion.

THC was consumed in 15 milliliter (mL) dosesequivalent
to one tablespoon (0.6 mg in 20 mL)of four different blends
of hemp and canola oils. The table shows the daily THC doses
administered during the study and the corresponding amounts of
hemp oil and hulled seedscontaining 5 and 2 ppm THC,
respectivelythat would have to be eaten to ingest the same
amounts of THC.

Urine samples were collected prior to the first ingestion of
oil (baseline sample), on days 9 and 10 of each of the four
study periods, and 1 and 3 days after the last ingestion. All
samples were analyzed for cannabinoids by radioimmunoassay (RIA),
confirmed for THCCOOH by gas chromatography-mass spectrometry
(GC/MS), and analyzed for creatinine to identify dilute samples.

Analysis of the collected urine samples showed that even
extended ingestion of up to 0.45 mg/day of THC is not likely to
cause interference with federal drug-testing programs. The table
shows that this daily dose of THC translates
into the daily eating of 6 tablespoons of hemp oil or half a
pound of hulled hemp seeds of commercial quality. Even hemp food
connoisseurs rarely consume such quantities. At this dose,
none of the volunteers exceeded the 50 parts per billion (ppb)
cutoff for the immunoassay screening test, applied by federal
workplace drug-testing programs. Confirmation by GC/MS
consistently found THCCOOH levels of less than 5 ppbi.e.,
considerably below the 15 ppb confirmation cutoff. The highest
THCCOOH level measured in a single sample was 5.2 ppb.

THC doses as low as 0.2 mg/day caused several exceedances of
the lower, more stringent, 20 ppb screening cutoff used by few
employers and law enforcement agencies. Yet GC/MS confirmation
found less than 5 ppb of THCCOOH in all of these samples. One of
three volunteers consuming up to 0.6 mg/day of THC screened
positive at the 50 ppb level, but was also confirmed at less than
5 ppb.

These findings suggest that even extended ingestion of
considerable quantities of currently available hemp foods is not
likely to produce urine samples that exceed the 50 ppb cutoff in
the immunoassay screening test and a 10 or 15 ppb confirmation
cutoff. The occurrence of screening positives at the 20 ppb
cutoff is conceivable. However, their confirmation by GC/MS at
the 10 or even 15 ppb cutoff is even less likely. Thus programs
following the federal testing guidelines are unlikely to
encounter confirmed positive samples for marijuana. On the other
hand, programs that rely entirely on the use of screening tests
with a low cutoff of 20 ppb and no automatic confirmation of
screening positives by GC/MS may occasionally encounter
unconfirmed positive samples from consumers of hemp foods.

In summary, this studys findings indicate that the
following measures will be effective in virtually eliminating
interference between consumption of hemp food products and
workplace drug testing:

Adherence by hemp food processors to seed cleaning and
quality control measures aimed at limiting concentrations
of total THC in hemp oil to 5 µg/gor ppmand,
in hulled seeds, to 2 µg/g.

Adherence of U.S. employers and administrators of
drug-testing programs to guidelines for federal programs,
requiring that urine samples that fail a screening test
be confirmed by GC/MS.

A detailed description of the studys design and results
is being submitted for publication in a peer-reviewed journal. It
will be posted at www.naihc.org following its publication.

Acknowledgments

Significant input to the design and interpretation of this
study was provided by the members of its scientific advisory
board: Dr. Rudolf Brenneisen, University of Bern, Switzerland;
Dr. Mahmoud ElSohly, ElSohly Laboratories, Inc., Oxford,
Mississippi; Dr. Franjo Grotenhermen, nova Institut, Cologne,
Germany; Dr. Harold Kalant, Addiction Research Foundation,
University of Toronto, Ontario, Canada; and Paul Mahlberg,
University of Indiana, Bloomington, Indiana. We are
particularly thankful for their contributions.

Valuable support to the experimental design of the study with
respect to the preparation and use of the oil was provided by G.
R. Barry Webster of Websar Laboratories, Inc., Ste. Anne,
Manitoba, Canada. We also thank Randall C. Baselt of Chemical
Toxicology Institute, Foster City, California, for his input to
the design of the study, particularly the design and quality
control of urine analysis.

Finally, the authors wish to express their particular
gratitude to the volunteers, whose reliable observation and
documentation of the prescribed oil consumption and urine
sampling regimen were essential to the data quality of this
study.